Efficient methods to identify and evaluate particular cell types would be useful in a wide variety of applications. For instance, cellular diagnostic testing, e.g., the diagnosis of disease states based upon the presence or absence of certain cell types, ideally utilizes testing protocols that can provide both speed and accuracy, as well as ease of use. By way of example, cancer, which is the world's deadliest and most costly disease requires the accurate recognition of the presence of cancer cells for proper diagnosis. Moreover, as early diagnosis can be key in improved survival rates, testing protocols that can recognize cancer cells at very low concentration are of great benefit.
While current cancer testing protocols such as histology/cytology testing, immunoassays, flow cytometry, and so forth have improved cancer screening and cancer survival rates, room for improvement in the art exists. For example, many testing protocols require multiple expensive tests to make a confident diagnosis, and protocols often lack high reliability. Testing methods are often complicated and require complex procedures that can increase prices. In addition, testing often is inadequate to distinguish the state of a cancer, for instance failing in distinguishing benign cancer cells from malignant cancer cells. Thus, a reliable and inexpensive device and method that could identify diseased cells in a test sample would be of great benefit.
The ability to quickly and reliably identify particular cell types and/or subpopulations of particular cell types would be of benefit in other applications as well. For instance, a major limitation in developing tissue engineered constructs is the ability to identify and isolate functional cells, typically progenitor cells, from the patient or donor. The ability to reliably and accurately test the function and the cellular make-up of transplant tissue would also be of great benefit to, e.g., prevent the transplant of diseased tissue. Conventional methods to identify and isolate desirable functional cells involve using cell surface markers and morphological traits as well as cell plating and cell adherence methods. However, many cell types lack common markers or universal morphological traits, making reliable testing extremely difficult. Conventional methods are expensive and do not directly evaluate cell function.
The development of engineered tissue constructs faces other difficulties, in addition to identification and utilization of desired progenitor cells. For example, there are currently constraints on the size of tissue constructs that can be created, and a major shortcoming of tissue engineering is that the size of the grafts that can be generated is small relative to the size of the defects that they are meant to treat. For example, autologous osteochondral grafting or mosaicplasty, often referred to as the gold standard for the treatment of cartilage defects and osteoarthritis, fails in the therapy of large lesions measuring more than about 20 millimeters in diameter, and the viable constructs formed to date are considerably smaller than this size.
The size constraints that tissue engineering currently faces are largely due to the non-homogeneous growth of cells on the traditional ‘porous block’ scaffolds, which prevents the formation of a functional construct from surface to core. This is due to two major limiting factors: lack of uniform cell seeding though the entire thickness of the scaffold and the mass transfer limitations of nutrients and waste removal. Because of the complex architecture of many 3D scaffolds, dispersing a high density of cells with high efficiency and uniformity throughout the scaffold volume is difficult. An additional factor in the survival of thick 3D engineered tissues is the delivery of oxygen and nutrients to the entire construct, and waste removal from the construct. The movement of nutrients to the cells and removal of waste products from the cells has to rely on molecular diffusion due to the lack of a vascular system. As such, nutrients are depleted before reaching the inner core of the construct and waste products accumulate. Cells that migrate into the core become necrotic and the living cell population is commonly concentrated at the periphery of the scaffold. There is also a delay in tissue formation or lack of tissue formation in the center of the scaffold due to the lack of biomolecule/growth factor penetration. An example commonly occurs in posterolateral fusions there is a “lag effect” of bone formation in the center of the scaffold.
What are needed in the art are devices and methods that can transport biological materials effectively. For instance, a device that can transport different cell types at different rates would be beneficial to provide a low cost, fast, and accurate cell recognition protocol. Additionally, a device that can transport biological materials such as cells, nutrients, biomolecules, and waste in a fast and efficient manner would be of benefit in tissue engineering.